Telegraph system



Feb. 23, 1937. v. P. THORP TELEGRAPH SYSTEM Filed March 15, 1935 INVENTOR Vi? Thai 70 BY ATTORNEY Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE TELEGRAPH SYSTEM Application March 15, 1935, Serial No. 11,349

4 Claims.

This invention relates to telegraph systems and, more particularly, to a method and means for controlling the transmission of signals over such systems.

The arrangements of the invention are particularly adapted for use in telegraph systems in which currents of carrier frequencies are utilized for the transmission of signals. In carrier telegraph systems used heretofore, it has been customary to control the outgoing carrier current by means of an electromagnetic relay having stationary contacts and a movable armature. Troubles have often been experienced with relays of this type, necessitating expensive maintenance of the relay adjustment, cleaning of contacts, etc. invention, the electromagnetic sending relay ordinarily used in carrier current telegraphy is done away with and a gas-filled discharge tube and circuit arrangements therefor are utilized to control the sending of signals over the system. Such an arrangement will require very little attention, will operate at higher speeds and will not get out of adjustment. While the arrangements of the invention are particularly adapted for use in carrier current telegraph systems, they might be also used for the control of any alternating current outgoing to a line by means of direct current without the use of an electromagnetic relay, Other objects and features of the invention will appear more fully in the detailed description thereof hereinafter given.

The invention may be more fully understood from the following description, together with the accompanying drawing, in which is shown a circuit diagram embodying a preferred form of the invention.

In the drawing is shown one terminal of a carrier current telegraph system. Signals would come in from a distant station over the line L2. This line might include a receiving filter 4, an amplifier 5, a detector 6 and a receiving relay I. The receiving relay I would be connected to the subscribers loop circuit I2 which would be of the balanced loop type. The subscribers loop circuit would include the sounder S, transmitting key K1, the equal resistance arms R and R and the resistances R2, R3, R4 and the battery B1. Connected to the junction point of the resistance arms R and R would be the armature of the receiving relay with which would be associated contacts leading to the marking and spacing batteries B2 and B3, respectively. For transmission of signals to the distant station,

In the arrangements of this 1 the line L1 is provided. This line would include the sending filter 3 and a generator G for'gen crating suitable carrier frequency currents. The carrier current produced by the generator G would flow freely through the resistances R5 and 5 Rs into the sending filter 3 to the line L1" provided winding I of transformer T, which is bridged across the line, presents a small shunt loss to the circuit. If, however, winding I of transformer I presents a low impedance path 10 to the flow of carrier current, there will be a large fiow of current in that winding and a corresponding large drop of carrier voltage applied to the sending filter due to the drop across resistance R5. Under this condition, the outgoing carrier current is reduced to a small value and a spacing signal may be transmitted to the line.

Means whereby the winding I of the transformer T is made to present either a large or small loss to the outgoing carrier current so that the transmission of signals may be controlled is the gas-filled discharge tube V and the circuits therefor. The secondary winding of the transformer is connected in series with the 5 filament and plate of the tube V. The filament and plate of the tube V are connected across the points A and B of the subscribers loop circuit.

The method whereby the operation of the gasfilled discharge tube V controls the impedance of the winding I of transformer T will now be described. The subscribers loop circuit I2, as heretofore pointed out, consists of the well known balanced loop type arrangement with certain modifications for the purpose of actuating the gas-filled tube V. The armature of the receiving relay is connected to the midpoint of resistances R and R. The resistance from this midpoint over the upper branch or arm of the subscribers loop, which includes resistance R2, sounder S, resistance R1, battery B1 to ground, is practicaly equal to the resistance of the other branch or arm of the loop including resistance R3 to ground. This may be arranged by proper adjustment of the resistances. When the receiving relay is on its marking contact and key K1 is closed, about sixty milliamperes of current will flow from battery B1 through resistance R4, sounder S, resistance R2, resistance R, battery B2 to ground. This is due to the fact that the batteries B1 and B2 are so connected as to be an aid to each other. At the same time, current of about thirty milliamperes will fiow from ground through resistance R3, resistance R, battery B2 to ground. In other words, twice as much current will fiow through the upper branch or arm of the loop circuit as will flow through the lower branch or arm of the loop circuit. Under these conditions there will be a difference of potential between the points A and B and point A will be positive with respect to point B. This is the condition for transmitting a marking signal. When the key K is opened, there will be no current in the upper branch or arm of the loop circuit but the current in the lower branch or arm of the loop circuit will continue in the same direction and with the same magnitude as before. Under this condition, the potential difierence across points A and B will be equal in value but reversed in polarity as compared to the case when key K1 is closed. In other words, when key K1 is opened or closed, reversals of polarity occur across points A and B.

Point A is connected through winding 2 of tranformer T to the cathode of the gas-filled discharge tube V. Point B is connected to the anode of the tube'V. A battery B4 is provided between the grid and cathode of tube V for adjustment --.of the point at which a discharge will take place :between the cathode and anode of tube V, if desired. 1 When point B is negative with respect to point A, the plate of the tube will be negative with respect to the cathode, and no discharge can take the relatively low impedances R, R and V in se- 3 and line L1 and thence to the distant station. When key K1 is opened, point B becomes positive with respect to point A, as previously described. This will cause the plate of the tube V to become positive with respect to the cathode and a dischargewill take place between the anode and cathode of tube V. When a discharge occurs in the tube V, the impedance between the anode and cathode becomes very low. Under this condition, transformer T is substantially short-circuited by "ries. When this condition exists, the carrier ourrent to the line L1 is substantially cut off and a spacing signal is transmitted to the line L1 and thence to the distant station. Accordingly, it will "be seen that the outgoing carrier current from the generator G may be interrupted and controlled in accordance with the operation of the subscribers key K1.

-When signals are being received from the line L2, the key K1 is kept closed. Accordingly, when embodiment in many and widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

l. A telegraph system comprising a transmitting circuit and a receiving circuit terminating at a station and a subscribers loop circuit, said loop circuit being of the balanced loop type and comprising two equal resistance arms, a receiving relay having a winding connected to opposite ends of said equal resistance arms and its armature connected to the junction point of said resistance arms, marking and. spacing batteries of different polarities connected to the contacts of said receiving relay, a transmitting key and a battery in circuit with one of said resistance arms, whereby when said key is closed one of the ends of said resistance arms will be positive in polarity with respect to the opposite ends of the other and when said key is opened this condition will be reversed, a gas filled discharge tube having its filament and plate electrodes connected to opposite ends of said resistance arms whereby the operation and release of said tube may be controlled by the polar .ity relationship between opposite ends of resistance arms, and means controlled by said tube for controlling said sending circuit.

2. A telegraph system comprising a transmitting circuit and a receiving circuit terminating at a station and a subscribers loop circuit, said loop circuit being of the balanced loop type and comprising two equal resistance arms, a receiving relay having a winding connected to opposite ends of said equal resistance arms and its armature connected to the junction point of said resistance arms, marking and spacing batteries of different polarities connected to the contacts of said receiving relay, a transmitting key and a battery in circuit with one of said resistance arms, whereby when said key is closed one of the ends of said resistance arms will be positive in polarity with respect to the opposite end of the other and when said key is opened this condition will be reversed, and whereby when said key is closed the connection of either said marking or said spacing batteries to said resistance arms will not change the existing polarity relationship between opposite ends thereof, a gas-filled discharge tube having its filament and plate electrodes connected to opposite ends of said resistance arms whereby the operation and release of said tube may be controlled by the polarity relationship between opposite ends of said resistance arms, and means controlled by said tube for controlling said sending circuit.

3. A telegraph system comprising a transmitting circuit and a receiving circuit terminating at a station and a subscribers loop circuit, said loop circuit being of the balanced loop type and comprising two equal resistance arms, a receivdifferent polarities connected to the contacts of said receiving relay, a transmitting key and a battery in circuit with one of said resistance arms, whereby when said key is closed one of the ends of said resistance arms will be positive in polarity with respect to the opposite end of the other and when said key is opened this condition will be reversed, and whereby when said key is closed the connection of either said marking or said spacing batteries to said resistance arms will not change the existing polarity relationship between them, a gas filled discharge tube having its filament and plate electrodes connected to opposite ends of said resistance arms whereby the operation and release of said tube may be controlled by the polarity relationship between opposite ends of said resistance arms, and a transformer having its primary winding bridged across said sending circuit and its secondary winding connected in circuit with the filament and plate of said tube whereby when said tube is operated the impedance of said transformer in shunt of said sending circuit may be varied to control the flow of signal current thereover.

4. A telegraph system comprising a transmitting circuit and a receiving circuit terminating at a station and a subscribers loop circuit, said loop circuit being of the balanced loop type and comprising two equal resistance arms, transmitting apparatus in circuit with one of said arms, means controlled by the operation of said transmitting apparatus for reversing the polarity relationship between opposite ends of said resistance arms, a gas filled discharge tube so connected to opposite ends of said resistance arms that its operation and release may be controlled by the polarity relationship between opposite ends of said resistance arms, a generator of carrier frequency signals connected to said sending circuit, an impedance shunted across said sending circuit, and means controlled by said tube for varying said impedance.

VAUGHN PENFOLD THOR? 

